The prevalence of and factors related to reinfection with COVID‐19 in Ahvaz, Iran: A comparative cross‐sectional study

Abstract Background and Aims Reinfection with the coronavirus disease 2019 (COVID‐19) virus may be as serious as the first infection, exposing people to risks such as admission to hospital or even death. This study aimed to evaluate the prevalence of and the factors related to reinfection in Ahvaz, Iran. Methods This was a comparative cross‐sectional study that was conducted on 200 reinfected individuals and 200 people who had once been infected with COVID‐19. Infection with COVID‐19 was confirmed using the polymerase chain reaction (PCR) test, and those with reinfection had to have a negative PCR test after recovery from the first infection and a positive PCR test for COVID‐19 > 90 days after the first infection. Data was collected using a questionnaire and a checklist. Data were analyzed using the Chi‐square test, independent t‐test, and logistic regression test. Results Around 7000 reinfections were observed in this study, and the prevalence of reinfection was 0.59% in Ahvaz City. A large proportion of the participants in the control group, 133 (66.5%) received two doses of COVID‐19 vaccines compared with 110 (55%) in the reinfected group (p = 0.003), and 43 (21.5%) of reinfected participants did not receive any vaccine. Older people were 0.982 times more likely to get reinfected with COVID‐19 (95% confidence interval [CI]: 0.966–0.997). Also, those receiving vaccination once or twice were 2.311 and 2.498 times less likely to get reinfected with COVID‐19, respectively (95% CI: 1.093–4.887 and 1.281–4.872, respectively). Conclusion The findings of this study showed that the prevalence of reinfection among people in Ahvaz City was 0.59%. Older individuals, those without vaccination or with suboptimal vaccination, and people with comorbidities were at a higher risk for reinfection. Health policymakers should pay more attention to factors related to reinfection with COVID‐19.


| INTRODUCTION
The first cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were identified in Wuhan, China in December 2019, and soon after, the virus spread to other places in the world. 1 In Iran, the first case of COVID-19 infection was reported in February 2020 in Qom city. 2 After thousands of deaths from the infection caused by SARS-CoV-2, the World Health Organization announced SARS-CoV-2 as a pandemic in 2020. 3 According to the latest reports, 7,565,367 people have thus far been infected with COVID-19 in Iran, of whom 144,779 have died. 4 Developed countries, such as the United States started vaccination in less than one year after the start of the pandemic, while countries such as Iran resisted to import vaccines from other countries and hoped to defeat the disease with homegrown vaccines. 5 Reinfection with COVID-19 virus may be as serious as the first infection. Vaccination played an important role in softening the impact of reinfection and the long-term complications of the disease. 6 A study in Iran showed that among 1492 individuals with confirmed COVID-19 infection, the rate of reinfection was 0.33% in 1-year follow-up. 7 In a retrospective study by Tavakoli et al. 8 on 213,768 patients with confirmed the polymerase chain reaction (PCR) test, the rate of reinfection was 0.97%, and 66.6% of the reinfected participants had their second positive test 90 days after the first infection, with the higher chance for reinfection being observed among men, urban population, adolescents and health care providers. Rahman et al. 9 found that individuals who get naturally infected were less likely to be reinfected compared to those who received vaccines. Sacco et al. 10 Adult individuals who had been reinfected with COVID-19 based on PCR   test and from whose primary infection at least 90 days had passed based   on the confirmation of an infectious disease specialist were recruited for this study. Furthermore, individuals with reinfection remained asymptomatic between the first and second infection and they had negative PCR tests. Individuals who had once been infected with the disease were recruited as the control group. Participants who claimed being reinfected but had no definite laboratory tests and those who were reinfected and then passed away were excluded from the study.

| Procedure
The list of patients with COVID-19 re-infection was prepared from the Deputy of Health of Ahvaz Jundishapur University of Medical Sciences. Those who had two confirmed PCR tests with at least a 90-day interval were selected. These individuals had a negative PCR test after recovery from their first infection, but then after at least 90 days, had a positive PCR test confirming their second infection. 13 People who had been once infected were considered as a control group. Both groups received a phone call inviting them to attend a public health center to complete a questionnaire and a checklist.

| Statistics
Data analysis was done using IBM SPSS Statistics (version 23). 14 Chisquare test and independent t-test (two sided) were used to compare categorical and continuous data, respectively. Logistic regression was used for testing the relationship between demographic characteristics and reinfection with COVID-19. p < 0.05 was considered statistically significant.

| RESULTS
This study was conducted in Ahvaz, the capital of Khuzestan province, southwest of Iran. The population of Khuzestan province is 4,711,000, and the population of Ahvaz is 1.185,000 according to the latest census. 15 From the beginning of the COVID-19 pandemic until September 2022, 533,000 individuals had been infected with COVID-19 in the Khuzestan province, of whom 26,000 individuals were reinfected, which indicates a reinfection prevalence of 0.55%.
Ahvaz accounts for around 7000 cases of reinfection, indicating a reinfection prevalence of 0.59% ( Figure 1).  were cough/shortness of breath with a frequency of 40% and 29.5% in the reinfected and control groups, respectively. Table 3 shows the factors related to COVID-19 infection in two groups of the reinfected and the control. Duration of the disease was significantly shorter in the second infection in the group of reinfection (p < 0.001). Admission to hospital and duration of hospitalization were significantly different between the two groups.
Most participants claimed that they had experienced less severe symptoms in the reinfection period.
The relationship of reinfection with some demographic factors was assessed using logistic regression, and the results are presented in provide permanent immunity, and there is always a possibility of reinfection. 16 Therefore, studying the prevalence of reinfection and its associated factors is of paramount importance.
The results of the present study showed that the prevalence of reinfection in Ahvaz City was 0.59%. Tavakoli  writing-review & editing.

ACKNOWLEDGMENTS
The expenses of this study were provided by Ahvaz Jundishapur University of Medical Sciences. The funder did not have any role in the design, data collection, data analysis, and interpretation, and writing and submitting the manuscript to a journal. We would like to thank all patients who participated in this study.

CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT
DATA of this study will be available upon the reasonable request from the corresponding author. The data used in this manuscript will be available upon the request from corresponding author.

TRANSPARENCY STATEMENT
The lead author Poorandokht Afshari affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.